A known rotor includes a rotary shaft (shaft member) supported by a casing made of resin around an axis of the rotary shaft. Fluid is fed, for example, to an engine by a turning force of the rotor. When an electric fluid pump including such rotor is used for many years, a bending moment, a turning force, and a pulling force act on a connecting portion between the rotary shaft and the casing, therefore decreasing a connecting strength of the connecting portion and causing the rotary shaft to be loosened and detached from the casing. A known connecting mechanism by which a rotary shaft is firmly fixed to a casing made of, for example, resin is disclosed in JP2002-147256A (hereinafter referred to as Patent Document 1). According to the connecting mechanism disclosed in Patent Document 1, the rotary shaft includes an end portion embedded in the resin so as to be fixed thereto and recessed and convex portions are formed on a surface of the end portion of the rotary shaft in such a way that a spiral groove is formed around an axis of the rotary shaft. The recessed and convex shapes of the surface of the rotary shaft improve an engaging ability of the rotary shaft with the resin.
However, according to Patent Document 1, since the connecting strength of the connecting portion between the rotary shaft and the casing depends on the recessed and convex shapes of the surface of the rotary shaft, the rotor is not surely resistive against a turning force applied to the rotary shaft. That is, a resisting force of the connecting portion is determined by an outer diameter of the rotary shaft and the rotary shaft may be gradually loosened from the casing as the rotor is used for many years. Further, since an area of the surface of the end portion of the rotary shaft, which is resistive to the above-mentioned bending moment and pulling force, is small, the rotary shaft may be loosened and detached from the casing. Thus a firm connecting strength of the connecting portion between the rotary shaft and the casing is not surely obtained by the connecting mechanism disclosed in Patent Document 1.
Furthermore, when an axial length of the connecting portion between the rotary shaft and the resin casing is elongated, the connecting strength therebetween is increased; however, the electric fluid pump may be increased in the axial length.
Moreover, no standard for positioning the rotary shaft relative to the casing is established in Patent Document 1. For example, when the rotary shaft is inserted in a mold for insert-molding the casing with resin, the rotary shaft is required to be surely fixed to the mold. Thus the mold may require a complicated configuration. When the standard for positioning the rotary shaft relative to the casing is not established, the rotary shaft is inaccurately positioned in the mold, thereby deteriorating the operating accuracy of the rotor and causing vibrations of the rotor. As a result, a bending moment and a pulling force acting on the rotary shaft may be further increased.
A need thus exists for an electric fluid pump and a mold for insert-molding a casing of the electric fluid pump, which are not susceptible to the drawback mentioned above.